1. Field of the Invention
The invention relates to a process for the preparation of monoethanolamines by amination of ethylene oxide with ammonia using acid activated clay catalysts. These clays which have been treated with acid have particular properties which provide greatly enhanced reactor productivity while maintaining very high selectivity for monoethanolamine.
2. Description of the Related Art
Most of the efforts regarding the production of monoalkanolamines have been concerned with the manufacture of monoethanolamine (MEA) from the reaction of ammonia with ethylene oxide.
The Kirk-Othmer Encyclopedia of Chemical Technology, Third Edition describes the standard manufacture of MEA from the reaction of ethylene oxide with an excess of aqueous ammonia at a temperature of about 50.degree. to 100.degree. C., see Vol. 1, pp. 95-952 and Vol. 9, p. 437.
It was accepted for a long time, and originally demonstrated by Knorr in 1987, that a small proportion of water was essential to such a reaction since pure ethylene oxide does not react with anhydrous ammonia (Bev., 1987, Vol. 30, p. 909 and 1899, Vol. 32, p. 729). For a background on this reaction, showing a general acceptance that the presence of water was required, see Ellis, Carleton, The Chemistry of Petroleum Derivatives, New York: Reinhold, Vol. 1, pp. 541-544 (1934) and Vol. 2, pp. 563, 567 (1937) and Miller, S. A., Ethylene and Its Industrial Derivatives, London: Ernest Benn Limited, pp. 16-17; 22,632-635 (1969).
Acids have been used as catalysts or cocatalysts in a number of reactions described. U.S. Pat. No. 2,186,392 reveals that ethanolamines may be produced from ammonia or a primary amine and ethylene oxide and a salt of a weak acid, such as ammonium carbonate, in the presence of an aliphatic radical which is positive with respect to hydrogen. See Chemical Abstracts (CA) 36:4131-2. Tertiary amines with hydroxyalkyl radicals may be made from ammonia, primary or secondary amines and an alkylene oxide at a temperature of from 30.degree. to 60.degree. C., with improved yields being possible if water or a weak acid is also present. See German Patent No. 844,449 (CA 48:1429c). British Patent No. 497,093 teaches that monoalkanolamines may be made from olefin oxides and ammonia in the presence of water and an acid (see CA 36:4131-8).
Another catalyst which has been the object of research is aluminum oxide. M. Sile, et al in two articles titled "Catalyst Reaction of Ethylene Oxide with Ammonia", found that ethylene oxide and ammonia may be reacted together at high temperatures (350.degree.-700.degree. C.) over aluminum oxide, phosphate catalysts and 13X zeolites to yield a large number of products of which ethanolamines were only a small part, including pyridine, alpha- and gamma-picolines, acetic acid, piperazine, aziridine, diethylamine, ethylenediamine and dioxane, see Latv. PSR Zinat, Akad, Vestis, Kim. Serv., Vol. 1972, parts 1 and 2, pp. 54-60 and 218-23, respectively, (CA 77:5243f and 88175j). More specifically, aluminum oxide at 350.degree. to 450.degree. gives pyridine, alpha- and gamma-picolines, acetic acid, alpha-aminoethanol and dioxane; zeolite 13X at 388.degree. to 450.degree. gave instead pyridine, alpha- and gamma-picolines, dioxane, piperazine and a little ethylenimine, diethylamine and ethylenediamine while different phosphates gave pyridine, alpha- and gamma-picolines, acetic acid, alpha-aminoethanol and ethylenimine.
In other work it is taught that ethylene oxide and ammonia may be reacted together over aluminum oxide at 300.degree. to 350.degree. C. to produce ethanolamines and an aldehyde. See M. S. Malinonskii, J. Applied Chem. (USSR), Vol. 20, pp. 630-634 (1947).
U.S. Pat. No. 3,697,598 reveals a method by which monoalkanolamines may be made from excess ammonia and alkylene oxide without water in the presence of a cationic ion exchange resin at a temperature of at least 80.degree. to 150.degree. C. In Swedish Patent No. 158,167 to the same inventor, and referred to within the '598 patent, there is disclosed the reaction of alkylene oxides and ammonia in an anhydrous reaction system using as a catalyst organic and inorganic acids, ammonium salts and ion exchange resins. The advantage of such an anhydrous reaction is elimination of the water removal step. There is usually not as much stability at high temperatures with ion exchange resin catalysts as would be desirable. In addition, in some processes the selectivity to monoalkanolamines in proportion to di- and trialkanolamines is not as high as would be desirable.
In an article titled "Comparison of Some Solid Catalysts for the Production of Ethanolamines from Ammonia and Ethylene Oxide in the Liquid Phase", by L. Vamling and L. Cider in Ind. Eng. Chem. Res. Dev. 1986 (25) 424, there is a discussion of the ability of different forms of zeolites to catalyze the formation of mono- di-, and triethanolamines from ethylene oxide and ammonia in the liquid phase, as well as a comparison of zeolite catalysts with organic ion-exchange resins.
U.S. Pat. No. 4,438,281 discloses a method for selective production of monoalkanolamines from alkylene oxides and ammonia over acidic inorganic catalysts. Here the highest selectivity to monoethanolamine was 87%. The catalyst productivity was not as great as would be desirable, generally it is in the range of ca. 0.02-0.07 g MEA/cc/hr.
In an article titled "Catalysis: Selective Developments", Chem. Systems Report 84-3, 239-249, at Section 3.4320, the unusual properties of smectite clays which make them generally of interest as catalysts are discussed. These compositions are layered and exhibit a 2:1 relationship between tetrahedral and octahedral sites. In addition, the combination of cation exchange, intercalation and the fact that the distance between layers can be adjusted provide interesting possibilities.
There is a discussion of clay mineral catalysts, including "acid" montmorillonite clay catalysts in "Progress In Inorganic Chemistry", Vol. 35, p. 41 (1987). The process of pillaring this type of catalyst is discussed. The process of pillaring can convert a clay lamellar solid into a more heat resistant two dimensional zeolite material.
It would be a great advantage if a catalyst could be provided for production of monoalkanolamines which worked at very high space velocities and yet afforded high selectivities and yields with a smaller percentage of by-products. In addition it would be an advantage if the catalyst were stable at higher temperatures.